Recent studies on our laboratory have shown that pretreatment of mice with either oral or intraperitoneal vitamin A significantly protects these mice from the development of a transplanted, highly immunogenic melanoma. Further studies have suggested that this protection may be based upon nonspecific immune enhancement. Other studies have shown a certain percent of established melanomas will regress when injected directly with Vitamin A palmitate. In the future we plan to investigate more intersively the mechanism of action of Vitamin A and determine its relevance for other tumor systems.